Use another cell value to dictate the exact row no. value that is taken

Hello, as described in the title, I want a value of a cell to dictate the no.row in a column that i want to look to take as value in the calculation
Example: On the same last filled current row, I want my cell in column B to display a certain value from a row in column A, but which row it would be depends on the on the last filled current row value in cell C, and how much it looks up will be dictated by that same value in C. If C says "0" I use the current last filled value in A and put it in B, if C says another number, I go that number of rows up and take value from column A on that row.
If cell C in the current row says 0 , I take the lowest most recent value from row A and show it in B, if cell C contains "5" I take 6th row in A, starting from the lowest up.
Lets suppose we are on row no. 25 currently and for C25=0 > B25=A25, for C25=1 >B25=A24 , for C25=2 >B25=A23, for C25=3 >B25=A22 etc... I am always starting from lowest row so the bigger my C value is, the further up I go on the list of column A to take the value and put it in my current B row.
We can also start from 1 and not 0, if 0 cannot be used in the calculation, it will not be a big pain, if I have that logic implemented.
Lets hope I managed to describe what I want. Maybe it is simple but it is hard for me to put it in words and I dont know how to make an example sheet with that... Thanks for the help to the forum once again!